Particular is an adjective meaning "specific" or "special". It can also be used as a noun to refer to a detail or individual item.
Common usages of particular include:
1. She's very particular about her food. (meaning: picky or fussy)
2. I don't have any particular reason for doing this. (meaning: specific)
3. The police asked for particulars of the incident. (meaning: details)
4. This particular model is very popular. (meaning: specific)