The difference between primary and secondary cell in LTE is given below.
Primary Cell
The cell, operating on the primary frequency, in which the UE either performs the initial RRC connection establishment procedure or initiates the RRC connection re-establishment procedure, or the cell indicated as the primary cell in the handover procedure.
What is acceptable cell and suitable cell in LTE?
Secondary Cell
The concept of secondary cell came in LTE advanced feature that is carrier aggregation. A cell, operating on a secondary frequency, which may be configured once an RRC connection is established and which may be used to provide additional radio resources.