Balance

 

When topping up MQL5 services we see something like   Balance: 170.00 USD (locked: 120.00)

Is the locked amount part of the Balance amount or separate?

In other words in the above example do I have $170 available for use? Or $50 (170 minus 120)? 

 
Your 170.00 balance is the available amount, for using it in MQL5.com.
 
David Swann: When topping up MQL5 services we see something like   Balance: 170.00 USD (locked: 120.00)

Is the locked amount part of the Balance amount or separate? In other words in the above example do I have $170 available for use? Or $50 (170 minus 120)? 

Locked means that the amount is awaiting review and verification.

When topping up this may be due to a verification process under way. For money earned, it is in case there is a dispute or the customer requests a refund and that is usually 7 days for Market products and Freelance jobs as a developer that have been completed. For Freelance jobs as a developer, at some point during the process (I'm not sure if it is at the demo stage), the agreed value also become available as "locked".

Locked funds effectively means that you cannot use it. It is unavailable for anything at all. So, in your case only the $50 (170-120) is available to use to buy things (or for withdrawal if it is earned funds).