Every field has its shorthand, and digital marketing has more than most. In a single meeting you can hear CPA, CTR, LTV, and SERP without anyone pausing to define them. Here is a plain-English glossary of the acronyms you will actually run into, so the alphabet soup stops slowing you down.
CMS: Content Management System (software to create and edit web pages)
COS: Content Optimization System (a CMS built to optimize content for reach and conversion)
CPA: Cost per Action, also Cost per Acquisition
CPC: Cost per Click
CPL: Cost per Lead
CPM: Cost per Mille (cost per one thousand impressions)
CR: Conversion Rate
CRM: Customer Relationship Management (software)
CTA: Call to Action
CTR: Click-Through Rate
KPI: Key Performance Indicator
LTV: Lifetime Value (of a customer)
PPC: Pay per Click
PPL: Pay per Lead
PPS: Pay per Sale
PV: Page View
ROI: Return on Investment
SaaS: Software as a Service
SEO: Search Engine Optimization
SEM: Search Engine Marketing
SERP: Search Engine Results Page
SMM: Social Media Marketing