"ing" is used to indicate that you are doing the verb *right now*. In other words, it is the "Present Continuous" tense. For example, I am "writING" to you right now. I am "thinkING" about what to write to you right now. I am "answerING" your question right now. I am "typING" on the keyboard right now. :).
This is different from the "Present Perfect" tense -- in present perfect, it is an action that you do as a habit. For example, I "eat" breakfast in the morning. I "read" a book every day. I "watch" movies every evening.
Does that make sense now? :)