What is the difference between lead and lead-free solder?

Soldering is a process that combines metal parts by melting a metal filler material and allowing it to flow into the joint. Soldering is commonly used to join pipes and electrical components in plumbing and electrical work.

Solder - Wikipedia

Lead-Free Or Leaded Solder: What's Best

Low temperature lead free solder paste - SURFACE MOUNT PROCESS

Lead vs. Lead-free Solder: Which is better for PCB manufacturing?

Lead vs. Lead Free Solder: Is lead free solder better?

Lead free Solder and Your Equipment

Lead vs Lead-free Solder - An Ultimate Guide - NextPCB

What is a lead-free solder? - Quora

Lead Solder vs. Lead-Free Solder for PCBs

Lead Free Solder