Answer 1

Every language have it's advantages and disadvantages, some are slower some are faster, some are compiled (e.g c++)some are interpreted(e.g python). Some are suited for some applications better then other. For example python is very popular for scientific purposes while Java is a very popular choice for Android app development(among many other things).
As you have tagged html, its important to know that it's not a programming language but rather a Markup language, it's even in the name (Hyper Text Markup Language), we use it to describe the structure and content of a web page.