In JavaScript and PHP you can put any type of data into a variable and not worry about it.  In many other languages you have to specify the type of data.  You have seen this in SQL because databases are very strict about data types.  There are three or four very common data types:

There are many others so make sure you are using the correct data type when you use SQL and be aware of the concept that many programmers have to worry about data types but you don't for Web development programming.  The SQL data types you have not used yet can be easily researched when you need them.