BEFORE he played tennis - might make it clearer

If you mean had had - it is the past perfect form with the third form of 'have'. Past perfect always takes 'had', and here with the third form of 'have', which is also 'had'.

e.g

John had had lunch BEFORE playing tennis=

the past perfect form BEFORE another past action 

Compare:

John had eaten lunch BEFORE playing tennis 

John had had lunch BEFORE playing tennis

Both mean the same - but 'had had' does sound strange.

What is the meaning of the word "had"?  "Had" is the past tense of the verb "to have."  It can show possession or ownership - "She had a blue dress" - or it can indicate a past action - "I had lunch."  Sometimes, it can be used to show a former state of being - "Joe had a bad day."  In this last example, it is implied that Joe is no longer having a bad day. 

I hope this helps!