Hey, James! The thing with Spanish that doesn't happen that often in English is that we tend to use reflexive verbs a lot. And the funny thing is that both the normal verb as well as the reflexive verb are used interchangeably. So, for example:
"I laughed a lot." can be translated to both of these sentences:
"Me reí mucho."
"Reí mucho."
Both are grammatically correct, so no worries there, just in my experience, in Latin America we use the reflexive form "me reí" way more frequently than the normal "reí".
Another example so you get comfortable with both options would be:
"She slipped and almost fell, and couldn't stop laughing."
This can be translated to:
"Ella resbaló, y casi se cae, y no podía parar de reírse." ( reflexive form ) or
"Ella resbaló, y casi se cae, y no podía parar de reír." ( normal form )
Again, both are correct, but the reflexive form is more frequent, at least orally. The funny thing is that I chose this sentence without realizing that it's a great example of what I told you at the beginning. Both "slip" and "fall" can be used as normal verbs or as reflexive verbs in Spanish.
You can say "Se cayó" or simply "cayó", and you can say "se resbaló" or simply "resbaló". Both are possible.
Last but not least, when you use the preposition "de", it means "laugh at". But here's another funny fact, when you introduce "de" into a sentence, we almost always use the reflexive form "reírse". If you say "reir de" I guess it's possible but it sounds weird, at least to me. So, for example:
"The children laughed at him because he fell." would be translated to
"Los niños se rieron de él pues se cayó." In this case, in contrast with the former examples, I wouldn't say "Los niños rieron de él pues se cayó.", it may be grammatically correct, but it doesn't sound right.