Goliath's Spear

what is the difference between a spear and javelin?

I Samuel 17:4-7 “and a bronze javelin was slung on his back. The shaft of his spear was like a weaver's beam, and his spear's head weighed six hundred shekels of iron…”

A spear was used as a defensive weapon to jab and fight off an enemy in hand-to-hand combat. It was typically weighted and balanced to use with one hand near the middle so the other hand might utilize a shield, sword or javelin. The biggest difference between a spear and javelin is that a spear was meant to stay in the hands of the warrior, while a javelin was used as an offensive tool to throw. Javelins were much shorter, lighter and had smaller heads.

https://www.britannica.com/technology/military-technology/The-spear#ref521912