A conjunction links words or groups of words. Conjunctions are either coordinating or subordinating.

Coordinating conjunctions

Coordinating conjunctions join words and clauses that have an equal value. These are the most often used Lithuanian coordinating conjunctions:

ir and
bei and (ir is more often used than bei)
bet but
o and, but
tačiau however, but
ar or, whether
arba or

Man patinka obuoliai ir vyšnios. I like apples and cherries.
Tau patinka obuoliai, ananasai bei vyšnios. You like apples, pineapples and cherries.
Aš noriu šokolado, bet neturiu pinigų. I want chocolate, but I don't have money.
Man dešimt metų, o jam - dvidešimt. I'm 10 years old, and/but he's 20.
Aš suprantu prancūziškai, tačiau dar nemoku kalbėti. I understand French, however I can't speak it yet.
Valgysime grybų ar uogų? Are we going to eat mushrooms or berries?
Valgysime grybus arba uogas. We're going to eat mushrooms or berries.
Paklausk jo, ar mėgsta uogas. Ask him whether he likes berries.

Subordinating conjunctions

Subordinating conjunctions join dependent clauses to main clauses. These are the most popular subordinating conjunctions:

kad that, in order to
jog that (Kad is more popular than jog. Jog should be used when kad is said too much. Jog cannot be said as 'in order to'.)
kai when
kol while
jei, jeigu if
nes because (nes is used in the second clause of a sentence)
kadangi because, since (kadangi is used in the first clause of a sentence)
kaip how
nors although

Vakar sakiau, kad man patinka obuoliai. Yesterday I said that I like apples.
Vakar sakei, jog tau patinka bulvės. Yesterday you said that you like potatoes.
Sunkiai dirbu, kad nusipirkčiau obuolį. I work hard in order to buy an apple.
Kai buvau vaikas, bijojau baubų. When I was a child, I was afraid of ghosts.
Sutvarkyk kambarius, kol aš būsiu darbe. Clean the rooms while I'm at work.
Jei daug valgysi, būsi storas. If you eat a lot, you'll be fat.
Jeigu nedaug valgysi, būsi plonas. If you don't eat a lot, you'll be slim.
Jis skaito daug knygų, nes nori būti protingas. He reads lots of books, because he wants to be smart.
Kadangi nori būti protingas, jis skaito daug knygų. Since he wants to be smart, he reads lots of books.
Paklausk jos, kaip tarti šį žodį. Ask her how to pronounce this word.
Aš išlaukiau egzaminą, nors nesimokiau. I passed the exam, although I didn't study.

Some adverbs can also act as conjunctions, for example todėl (so), tada (then), tai (so and some more meanings).

Nieko nebuvo namie, tai suvalgiau obuolį. There was no one at home, so I ate an apple.
Parvažiavau namo, tada įsijungiau televizorių ir užmigau. I came back home, then I turned on the TV and I fell asleep.

These were the basics of Lithuanian conjunctions. Go back for some more grammar.