SEO commonly used terms

Google PageRank
SEO - (Search engine optimization)

SEM - (Search engine marketing)
On-Page optimisation
Off-Page optimisation 
Back-links
Spamming
PLR articles (Private label rights)
Alexa Ranking
Conversion Rate
Inbound Link 
Internal Link
Keyword Density
Long Tail Keyword 
PPC (Pay-Per-Click) 
Organic SEO
Search Engine Results Page (SERP)
Affiliate Marketing
B2B  - Business To Business
B2C  - Business To Consumer
CPA  - Cost Per Acquisition    
CPC  - Cost Per Click
CTR  - Click Through Rate. 

Keyword Density
Paid Link Building
Explanation of all terms soon.