Hold note
Hold notes (a.k.a. long notes) are notes that require you to hold and release them afterwards. They are often also referred to as "noodles" or "LNs" and are used to represent prolonged sounds in the music.
Releases refer to hold note ends, i.e. the part that requires the key to be released. They have special significance due to release timing being taken into consideration in the osu!mania judgment system.
Shield
Shields occur when a note is placed consecutively before a hold note in the same column. They play very similarly to minijacks.
Reverse shields occur when a consecutive note follows a hold note's release within the same column.
Inverse
Inverse is a type of hold note pattern in which all notes are replaced with hold notes that extend to right before the next one in the same column. This creates what looks like a wall of hold notes and forms dense patterning with heavier reliance on reading ability.