"Told" is used when there are necessarily two parties: a speaker and a listener.
✅"He told me", "you told your mother", "I tell you", etc. In the passive voice, the speaker might be just implicit, "I was told to do that (by someone)", "You were told to clean up this mess (by your girlfriend)".
⛔️Incorrect uses occur as in "I told a word", "You told many things last night", etc. when a listener is missing.
"Said" is used when just the speaker is mentioned.
✅"You said many things last night", "Because she said so", "I say let's go!" In the passive voice, both speaker and listener can go implicit, "It has been said".
⛔️Incorrect uses occur when you mention both speaker and listener "I said you", "You said her to leave", etc.
A same sentence can be written with either of the two:
✅You said we would stay together forever.
✅You told me we would stay together forever.
⛔️You said me we would stay together forever.
⛔️You told we would stay together forever,
But notice the "told" version requires to introduce a listener ;)