From the point of view of the spelling, Ь simply means "the previous consonant should be palatalized". See https://en.wikipedia.org/wiki/Palatalization_(phonetics) to learn what palatalization is, it's a lengthy topic (P.S. Yellow Sky has a nice overview). Most consonsants in Russian come in pairs: palatalized/non-palatalized (also called soft/hard). Additionally, before vowels, Ь means "y" (Воробьев => Vorobyov)

When it comes to morphology, -Ь is often found in cases where we have a null ending in words whose stems end in a palatalized consonant, example: путь. Also found in 2nd declension in nominative/accusative cases (of feminine gender) for historical reasons: ночь (consonant Ч is always palatalized, so no need to have Ь as a palatalization marker, but we still do).

-ь is also found, for example, as a morphological unit, in imperative word forms: брось! i.e. it tells that C is palatalized, witch matches with the palatalizedness of С in the original infinitive: бросить

In some cases, like -ешь in verbs (for 2nd person), the spelling is just historical, and Ь there doesn't mean anything anymore.

So, in a nutshell, you can think of Ь as yet another palatalizing vowel (similar to Е and И), except it's not actually pronunced, yet still has influence on surrounding sounds.

From the point of view of the spelling, Ь simply means "the previous consonant should be palatalized". See https://en.wikipedia.org/wiki/Palatalization_(phonetics) to learn what palatalization is, it's a lengthy topic (P.S. Yellow Sky has a nice overview). Most consonsants in Russian come in pairs: palatalized/non-palatalized (also called soft/hard). Additionally, before vowels, Ь means "y" (Воробьев => Vorobyov)

When it comes to morphology, -Ь is often found in cases where we have a null ending in words whose stems end in a palatalized consonant, example: путь. Also found in 2nd declension in nominative/accusative cases (of feminine gender) for historical reasons: ночь (consonant Ч is always palatalized, so no need to have Ь as a palatalization marker, but we still do).

-ь is also found, for example, as a morphological unit, in imperative word forms: брось! i.e. it tells that C is palatalized, witch matches with the palatalizedness of С in the original infinitive: бросить

In some cases, like -ешь in verbs (for 2nd person), the spelling is just historical, and Ь there doesn't mean anything anymore.

So, in a nutshell, you can think of Ь as yet another palatalizing vowel (similar to Е and И), except it's not actually pronounced, yet still has influence on surrounding sounds.