A CRM (customer relationship management system) is the software that holds a company's commercial memory: contacts, companies, deals, conversations, tasks. Done right, it answers "where does this deal stand and what happens next?" for anyone, instantly. Done wrong, it is a database salespeople resent updating.
The build-or-buy question has a real answer per company — custom CRM versus SaaS lays out the arithmetic, and our custom CRM service covers the build side.