This word has at least two different meanings.

talaga, adv
really, truly, indeed

Mahal kita talaga.
I truly love you.

Talagang talaga.
Really, truly. So much!

Talagang ganyan.
It’s really like that.

Talagang ganyan ang buhay.
Life is really like that.

A similar Tagalog word is totoo (true).

There is also another, unrelated meaning for the Tagalog word talag√°, accented differently. It is usually in conjugated form.

Nakatalaga sa tadhana.
Destined by fate. 
(Written in the stars.)

A similar-looking but unrelated Tagalog word is dalaga.