Vectors are the DNA molecules onto to which f.DNA can be cloned. There are two types of vectors
1. Cloning Vectors
2. Expression Vectors
Cloning vectors are those to propagate the f.DNA inserts.
Expression vectors are those, if the objective is to obtain the gene product (protein) from the inserted f.DNA. For expression vectors suitable regulatory sequence has to be provided, like Promoter, Repressor,Operator, Terminator, etc
Promoters are those which marks the starting on the gene which helps the binding of the RNA polymerase and there by the expression of the gene. Promoters are of two types Strong promoter & Weak promoter.

Strong Promotes- Which helps in high rate of gene expression
Weak promoter – which low level expression of the gene.

The Vectors:
Different vectors are available
examples:
pBR322:
Features
Size : 4.3kb
Markers:ampr, tetr
Restriction Sites: BamHI,HindIII, EcoRI,SalI,PstI,etc
Ori: Present