okuruz is "we read" used with biz (we).
okursunuz is "you read" used with siz (you, plural).
The verb okumak (to read) conjugated on verbix: http://verbix.com/webverbix/go.php?D1=31=okumak
The tense we are interested in is the Simple (Aorist) Tense, in the Affirmative, used as a Statement (don't worry about all the terms, I'm writing them just to point you to what I am looking at on the verbix page):
- ben okurum = I read
- sen okursun = you (singular) read
- o okur = (s)he reads
- biz okuruz = we read
- siz okursunuz = you (plural) read
- onlar okurlar = they read
Turkish is a pro-drop language, so the pronouns (ben, sen, o, biz, siz, onlar) can be omitted.
okurlar (they read) doesn't need the -lar if the pronoun onlar is used, because onlar already conveys the fact that it is a plural (so onlar okur is correct too), but when the verb is used without the pronoun it needs to be okurlar. (Is this true of biz and siz too? I don't recall, or I didn't find out.)
For comparison, here is yemek (to eat):
- ben yerim = I eat
- sen yersin = you (singular) eat
- o yer = (s)he eats
- biz yeriz = we eat
- siz yersiniz = you (plural) eat
- onlar yerler = they eat
(While I'm talking about verb suffixes ...)
If I recall correctly, the consonants in the suffix (-rim, -rsin, -r, -riz, -rsiniz, -rler) of the verb stay the same, but the vowel in the suffix follows 4 way harmony with the vowel found in the root of the verb. So with ben (I), the suffixes for verbs with vowels a/ı, e/i, o/u, ö/ü in the root (ye- has e, oku- has u) would respectively be: -rım, -rim, -rum, -rüm. This is why we see ben okurum with -rum and ben yerim with -rim. This turkishbasics site seems to support my recollection: http://turkishbasics.com/verbs/present-simple-tense.php
It has been a little while since I studied Turkish, and I have still only studied the basics. I looked around for a web site which would summarise the above, but I consider those I have found to be over-complicated in their explorations (I posted a link anyway, above), so have written from memory. I hope I have remembered correctly! If I haven't, please someone leave a comment with corrections; thanks!