Call waiting is a feature in your phone wherein you will be notified of incoming calls while during a call.

Call holding is a feature in your phone that allows you to place an active call on hold in order to make another one, or to answer another incoming call.

For Android phones:

        STEP 1: Tap the phone icon/widget to go the dialing screen.

        STEP 2: Tap the "menu" button which is on the lower left side of your phone, beside the Home button.

        STEP 3: Go to > Settings > Call > Call settings > Additional settings > Call waiting

        Step 4: Check the box to activate.

For iOS:

        STEP 1: Go to Settings > Phone > Call Waiting

        STEP 2: Slide the toggle in the right to activate

To put a call on hold, you must first activate your call waiting. Once activated, simply tap the hold button in the screen while you are in a call to put a call on hold.