Conjunctions are used to join words, phrases and clauses. For example :-

ਅਤੇ atē and
ਜਾਂ jāṃ or
ਕਿ ki that, or

Above are all conjunctions. Based on their use, conjunctions can be classified into two categories, as below:

Co-ordinate conjunctions:
  These conjunctions are used to join words, phrases, or independent clauses in compound sentences. These can connect words of various word classes like noun, pronoun, adjective, adverb, and verb. ਅਤੇ, ਤੇ and ਜਾਂ are acting as co-ordinate conjunctions in the following examples –

ਮੁੰਡਾ ਅਤੇ ਕੁਡ਼ੀ ਆਏ ਸੀ।
ਪੰਛੀ ਗੀਤ ਗਾ ਰਹੇ ਹਨ ਤੇ ਠੰਢੀ ਹਵਾ ਵਗ ਰਹੀ ਹੈ।
ਅੱਜ ਮੀਂਹ ਪਵੇਗਾ ਜਾਂ ਹਨੇਰੀ ਆਵੇਗੀ।

Punjabi co-ordinate conjunctions are :-

ਅਤੇ/ਤੇ atē/tē and
ਜਾਂ jāṃ or
ਪਰ par but
ਫਿਰ phir then
ਸਗੋਂ sagōṃ rather
ਪਰੰਤੂ parntū but, however
ਚਾਹੇ cāhē either, even if
ਨਾਲ਼ੇ nāḷē alongwith
ਇਸ ਲਈ is laī so
ਇਸ ਕਰਕੇ is karkē thats why
ਭਾਵੇਂ bhāvēṃ even though
ਫਿਰ ਵੀ phir vī yet

Subordinate conjunctions:
  These conjunctions are typically used to introduce dependent clauses in complex sentences. Dependent clause signifies incomplete thought for whose completion, an independent clause is required. Punjabi subordinate conjunctions are: 

ਜੇ if
ਉਂਞ uññ by the way
ਤਾਂ tāṃ then
ਕਿ ki that, or
ਜੋ who, which
ਜਿਹੜਾ jihṛā who, which
ਜਿਵੇਂ jivēṃ as
ਜਦੋਂ jadōṃ when

Correlative conjunctions:   Some co-ordinate conjunctions as: ਭਾਵੇਂ/ਫਿਰ ਵੀ , ਚਾਹੇ/ਫਿਰ ਵੀ can also be used as correlative conjunctions to join independent clauses in compound sentences. Relative pronouns also can be used as correlative conjunctions to join different clauses in complex sentences. For example :-  

ਜੋ/ਸੋ jō/sō who/that
ਜਿਹੜਾ/ਉਹ jihṛā/uh who/that