man bash

. filename [arguments]
source filename [arguments]
Read and execute commands from filename in the current shell environment and return the exit
status of the last command executed from filename. If filename does not contain a slash, filenames
in PATH are used to find the directory containing filename. The file searched for in PATH need not be exe‐
cutable. When bash is not in posix mode, the current directory is searched if no file is found in PATH.
If the sourcepath option to the shopt builtin command is turned off, the PATH is not searched. If any arguments
are supplied, they become the positional parameters when filename is executed. Otherwise the positional parameters
are unchanged. The return status is the status of the last command exited within the script
(0 if no commands are exe‐cuted), and false if filename is not found or cannot be read.