"Licensed and insured" means two specific things: the contractor holds a valid state or local contractor's license (requirements vary by state - some states license general contractors, others only specific trades), and carries general liability insurance (protecting the homeowner if something is damaged) and often workers' comp (protecting the homeowner if a worker is injured on their property).
Homeowners actively search this exact phrase before hiring anyone, and a surprising number of remodeler websites never mention licensing or insurance status at all. Adding a simple, clear statement of your license number and insurance coverage - not buried in the footer, but visible near your quote form - closes a trust gap most competitors leave open.