ref – https://www.englishclub.com/efl/articles/vocabulary/8-ways-to-use-the-preposition-by/

“by” + place

The meaning is: beside, at the side of, next to, close to

examples:

• The house (s) is (v) by a river.
• David (s) lives (v) by a train station.
• I(s) want (v) to live (infinitive-obj) [in a house by the sea] (adjective phrase).

“by” + method of transport

This structure describes how you travel somewhere.

by + train/car/boat/plane/taxi/bus/coach

examples:

• David(s) went(v) [to] Manchester by train (adverbial).
• I (s) go(v) [to] work (by car) (adverbial).
• My parents (s) go (v) [to] France (by boat) (adverbial).
• Our children (s) travelled (v) by plane.

“by” + method of communication

This structure describes how you communicate with someone.

by + telephone/post/email/fax

examples:

• I (s) spoke (v) [to] her (obj) (by telephone) (adverbial).
• I (s) will send(v) you (obj) the invoice (obj compl) (by post)(adverbial).
• They (s) confirm (v) the order (obj) (by email) (adverbial).

“by” + reflexive pronoun

by + myself, yourself, himself, herself, itself, ourselves, yourselves, themselves

This structure means to do something alone.

examples:

• I(s) enjoy(v) reading(obj) (by myself) (adverbial).
• Sarah (s) is (v) studying (obj) (by herself) (adverbial).
• Let’s (s) do (v) something (obj) (by ourselves) (adverbial).
• My parents (s) go (v) on holiday (obj) (by themselves) adverbial.