Each type of PLMN has specific purpose. The PLMN list are stored on SIM in elementary files (EFs). Each PLMN list type has purpose the name signify the purpose.
EHPLMN --> Equivalent Home PLMN list - Home PLMNs (opeartor may have multiple PLMNs)
UPLMNwAct --> User Controlled PLMN list with access technology, user preferred
OPLMNwAct --> Operator Controlled PLMN list with acess technology, operator prefered
PLMNs in above list are listed in order priority. They should selected in same priority order during PLMN selection.
FPLMN list --> Forbidden PLMN list, UE should not try to access PLMN in this list in automatic selection mode.
During PLMN selection each PLMN type has priority. Priority is as follows:
a) Last Registered PLMN
b) Home PLMNs or EHPLMN in priority order
c) UPLMN in priority order
d) OPLMN in priority order
e) Any Other PLMN found in random order.
Refer to 3GPP spec 23.122 for more details on PLMN selection process