Run 2 activities in parallel In Pega ?

Use the Queue instruction to start asynchronous execution of a second activity. This provides an alternative to the Call instruction, in situations where there is no need to wait for completion of the second activity, or where processing in parallel is feasible and beneficial

BRANCH -- Branching to another activity.Use the Branch instruction to cause the current activity to find another specified activity and branch to it without a return.When the branched activity ends, processing of the current activity ends also; no steps after the Branch step are executed.CALL -- Calling another activity
COLLECT -- Begin execution of a collection rule 
FLOW-NEW -- Start a flow execution
JAVA -- Using Java in an activity step
QUEUE -- Execute another activity asynchronously
RULE -- Using the Rule instruction to implement a custom rule type(Rule instruction is deprecated)

Note:  Rule instruction is deprecated. Instead, call the evaluate Rule activityUse the Rule instruction to cause the current activity to find another activity named evaluateRule that implements a custom rule type. When this instruction executes, control transfers to that activity.