et al. / etc.
And other people versus and other things.
Et al. means and others. It stands for people: Lee et al. Etc. means and other things. It stands for objects or ideas, not people. Put a period after al. Do not write Lee, Kim, etc. if Lee and Kim are people.
Examples
UseChen et al.
Usepens, keys, etc.
AvoidChen, Patel, etc.