regex - line begins with operator

This is character ^ and using this operator returns the lines that starts with given search term.
Example 1:

$ grep '^sam' namex.txt
samad
samuel

Example 2:

$ grep '^PASS' /etc/login.defs 
PASS_MAX_DAYS	99999
PASS_MIN_DAYS	0
PASS_WARN_AGE	7