Express Entry

are separate provincial Nominee programs going on for every province, once you get nominated by a province then you can apply via express entry
For Express Entry once you get selected and after your final submission it takes almost 2 to 3 months, while processing time for provincial nominee programs can vary, you can check on the website for a particular province.
The NOC is the authoritative resource on occupational information in Canada. NOC tools classify occupations with four digit codes according to skill type and skill level. The Express Entry program only accepts applications which belongs to NOC level O, A & B
Arranged Employment Offer is where a skilled worker applicant has a certain kind of job offer in place before applying to immigrate to Canada.
A permanent resident visa grants the privilege of living and working permanently in Canada. A Temporary resident visa is issued to a person with permanent residence outside of Canada, but who wishes to be in Canada on a temporary basis, for example tourism, medical treatment, business, temporary work or study.
Express Entry is basically an electronic processing system on Internet started from January 2015, for efficient processing of permanent residence applications.
Express Entry consists of all the three basic Permanent Immigration programmes, you just need to apply by making your profile on CIC website, the best program is automatically assigned to you according to the information entered by you.
If you get selected for Federal Skilled Worker Program then it is must for you unless you got post secondary education from Canada, if you get selected on other streams like Canadian Experience Class or Federal Skilled Trades Program then its not mandatory, yet you can do it to increase your points.
Your family can be included, family means spouse/common law partner and children of principle applicant
Once you submit your profile for the first stage, then you must start gathering the documents because after getting invitation, you only have 60 days and if you are not able to submit all the supporting documents in given days then you have to decline the invitation. supporting documents checklist will be given to you before submitting first stage profile.