Motsu or Aru?

Ｍy dictionary says that I can use both 持っています and 有ります for the present tense "to have/hold", but the dictionary never explains the differences between them. Can I use them interchangeably or are there some differences I need to consider?

Not completely interchangeably.

Things that you say "arimasu" and cannot say "motte imasu" that come immediately to mind are: time (時間） and family/family members (家族、妻、子供, etc.), and appetite (食欲), just as examples.

Things that you can say either, but maybe "arimasu" is used more is: knowledge (知識) and capabilities （迫ﾍ、技煤j- so manybe "arimasu" is used more for something that you have in the sense of "you are equipped with."

Otherwise, for things that you can "own" or "physically hold" "have (with you/on you)," "motte imasu" is used more often, but either can be used.