Everything exists on a continuum. It is normal to have insecurities. A person with no insecurities is probably hiding something or not being honest with themself. But if you have so many insecurities that you can't muster enough confidence to do the things that you want to do, then low self-esteem would be a likely bet.

BTW, people who can't admit to having any insecurities have low self-esteem too. People with good self-esteem can admit to their insecurities and other vulnerable spots.