Interpersonal skills are the life skills which we use every day to communicate and interact with other people, individually and in groups. They include traits like self-confidence, critical thinking, active listening, communication skills, delegation, and leadership.
According to the Portland Business Journal, interpersonal skills or people skills can be described as:

Having positive interpersonal skills increases the productivity in an organization as it effectively helps to reduce the number of conflicts. In informal situations, it allows communication to be easy and comfortable. People with good interpersonal skills can generally control the feelings that emerge in difficult situations and respond appropriately, instead of being buried by emotion. 

As an example of interpersonal skills, it is well recognized that communicating respect for other people or professionals will enable one to reduce conflict and increase participation or assistance in obtaining information or completing tasks.

Interpersonal communication is the process by which people exchange information, feelings, and meaning through verbal or face-to-face communication. Interpersonal communication is not just about what is actually said but how it is said and the non-verbal messages sent through tone of voice, facial expressions, gestures and body language. People with strong interpersonal communication skills are usually more successful in both their professional and personal lives. They are perceived as calm, confident and charismatic - qualities that are often endearing. Being aware of your interpersonal skills can help you improve and develop them.

The Johari Window is an important and effective tool to measure Interpersonal Skills. It allows for better understanding of self and thus provides a means for an individual to evolve. The Johari Window was developed by Joseph Luft and Harry Ingham and was first used in 1955. The dimensions of the Johari Window are representative of an individual's whole personality or psyche.

The Johari Window model gives a framework for understanding and improving self-awareness. Greater self-awareness can make you more effective in group tasks, improve your interpersonal skills and build better relationships.

Following are the main ideas behind the functioning of this tool:

Here's what the different segments mean:

1. Open / Free area - Known by Self, Known by Others: This area includes all information freely shared by you to others around you. Some information is unavoidably in the open area, such as your body shape, or eye colour. Other information such as your views, experience, and knowledge are divulged by simply spending time with you. The simple aim is to increase your open area, by decreasing the other three areas.
2. Blind area- Unknown by Self, Known by Others: This area is the "spinach on your teeth" information - you're blissfully unaware. If only someone would tell you! You can decrease your blind area by actively seeking feedback from people. Scary as it may seem, but consider the alternative of not knowing.
3. Hidden area- Known by Self, Unknown by Others: It's probably best to leave your skeletons in your closet. There is some personal information that is useful to share, which helps people better understand where you're coming from. It is a rare skill, to know what to tell and what not.
4. Unknown Area- Unknown by Self, Unknown by Others: People who lack experience or are low in self belief may have a large unknown area. Good managers explore this area of potential and bring out dormant skills, abilities and talents by providing learning opportunities and a mistake proof culture.

• The goal of the Johari Window is to enlarge the Open Area, without disclosing information that is too personal. The more your team members know about each other, the more productive, cooperative, and effective they'll be when working together.
• As information is shared, your Open Area expands vertically and your Hidden Area gets smaller. As your team members provide feedback about what they know or see about you, your Open Area expands horizontally, and Blind Area gets smaller.
• Implemented well, the process of give and take, sharing, and open communication builds trust within the group.
• People who have a large Open Area are usually very easy to talk to; they communicate honestly and openly with others, and they get along well with a group. People who have a very small Open Area are difficult to talk to; they seem closed off and uncommunicative, and they often don't work well with others.
• Some people might have a large Blind Area, with many issues that they haven't identified or dealt with. However, others can see these issues clearly. These people might have low self-esteem, or they may even have anger issues when working with others.