Dictionaries (user dictionaries and personal dictionaries) allow you to register proper nouns and technical terms to be reflected in translation results, as dictionary data. Dictionary data can be registered for nouns only.
apple -> りんご
orange -> みかん
Translation memories are functions that allows you to register a set phrase that you want to have reflected in translation results, or a sentence that is difficult to translate as source text and translated text pair. This will then be reflected in future translation results when translating the same sentence.
Good Morning -> おはようさん。
Good Evening -> お晩です。
Also refer to "Translation Tips".
Refer to "What are personal dictionaries?" for information on the matching order between user dictionaries, personal dictionaries, and translation memories.