When (A) ている is paired with 間（あいだ）に (B), it expresses that ‘(B) is happening/happened within the timeframe of (A)’. These events do not need to be related in any specific way, but the (B) action must happen somewhere within the duration of (A). This construction translates naturally as ‘during the time that (A), (B)’.

• ねえ、数（かぞ）えている間（あいだ）には話（はな）しかけるな。
  Hey, don't talk to me while I'm counting.
• 荷物（にもつ）を運（はこ）んでいる間（あいだ）に転（ころ）んで怪我（けが）をした。
  I tripped and hurt myself when I was carrying luggage.

ている間（あいだ）に will often be used when the (B) action is somehow beyond the control of the speaker. However, this is not always the case.

• 旅行（りょこう）に行（い）っている間（あいだ）に家（いえ）に泥棒（どろぼう）が入（はい）った。
  While I was on a trip, a burglar came into my house.