- DEFINING (especificativas in Spanish): they help to identify or remark the noun which is referring to; e.g. That's the person who works with me at school.
 
- NON-DEFINING (explicativas): these go between commas and it's just an explanation or a comment about the noun; e.g. The tall girl, who works with me at school, plays basket.
 
If you need further explanation you may use these links: this is the first one but you can use this other
Once you are sure how to use them, let's practise qith these exercises:
Remember we use this kind of sentences very often:
- The person I admire most is ...
 - Something that I can't stand is ...
 - A screwdriver is a tool you use to fix screws or repair things
 - A place where I used to go was ...
 - I've lived in Meco, which is a village near Alcala, for almost 20 years
 - I can't speak French, which is a pity as I go to Paris quite often