Adverb particles are words like up, off, in, down and out, used as part of a phrasal verb.
He walked away.
Many words of this kind can be used as both adverb particles and prepositions, but there are some exceptions.
Examples are: back, away (only adverb particles); from, during (only prepositions).
When words like these are used as prepositions, they have objects. Adverb particles do not take objects after them.
She jumped down (preposition) the stairs (objective).
Please sit down (adverb particle).
Adverbs particles often join together with verbs to make two-word verbs. These are often called phrasal verbs.
Could you switch off the light?