How to use in & on

[leeds]

Sometime I'm confusing to use IN & ON, for example:

He is on a call, he is in a meeting. talking in to person or talking on to a person.

Thank You!

[bhaisahab]

Sometime I'm confused when to use IN & ON, for example:

He is on a call, he is in a meeting. These are both fine. Talking in to a person or talking on to a person. Neither "in" nor "on" is necessary in these two examples.

Thank You!

Bhai.

[leeds]

Thank you for the reply, can you explain how to use these two words, what are the conditions?