What is the meaning of 's and whe I use it?

Do you usually use the reported speech?

First notebook entry: Introducing myself I'm here because I want to improve my english, in special my pronunciation,so my principal objective is to practise my speaking and in the same way I could know people from other countries and diferent countries. I forgot to mention that I'm learning english and anybody who knows this language will be usefull for my learning. I'm from Colombia, but really I don't know the gramatic rules of spanish but I know how to speak spanish because is my native language, so if I could help anybody with this language is my pleasure, and I could talk with anyone about my country, my live, my hobbies, my culture and any kind of topic to help people to understand how is my country. I appreciate your comments and corrections.