You may want to create your own note type if you need to use a specific type of private data or struct that is not already implemented in Aztec.nr, or if you want to experiment with custom note hashing and nullifier schemes. For custom hashing and nullifier schemes, use the #[custom_note] macro instead of #[note], as it does not automatically derive the NoteHash trait.
Note discovery refers to the process of a user identifying and decrypting the encrypted notes that belong to them.
Notes are the fundamental data structure in Aztec when working with private state. Using Aztec.nr, developers can define note types which allow flexibility in how notes are stored and nullified.
The state model page explains that there is a difference between public and private state. Private state uses UTXOs (unspent transaction ouputs), also known as notes. This page introduces the concept of UTXOs and how notes are abstracted on Aztec.
Describes how partial notes are used in Aztec
Address notes hold one main property of the type AztecAddress. It also holds owner and randomness, similar to other note types.
ValueNotes hold one main property - a value - and have utils useful for manipulating this value, such as incrementing and decrementing it similarly to an integer.
Core knowledge of Notes and how they work