Welding cable typically consists of a single, finely stranded conductor that ranges in size from 8 AWG to 500 kcmil and a single layer of EPDM or neoprene thermoset insulation with an operating temperature rating of 90°C or 105°C. Welding cable is thermoset (as opposed to thermoplastic) to better resist weld splatter.
Properly rated welding cables can replace battery cables, but not vice versa. While it is not necessary to replace battery cables with welder's, it is an option if you need a flexible cable with a higher voltage than a regular battery cable. Welding lead wire works for car batteries as well.