Hey,
Well,yes you are eligible for admission in colleges for undergraduate courses post your 12th provided you meet the eligibility criteria of that scope which definitely includes you passing 12th.You may apply for central universities or Private universities which either take admission on the basis of marks scored in 12th or entrance exams.
A large ocean of opportunities awaits you once you are done with your high school. It all depends on  your calling .So first be sure of what you actually want to do in life. It depends upon the subjects you studied in 12th.If you were from Science then you can go for Engineering for that you will have to take the entrance exams for instance JEE Mains,WB JEE etcetera.You may go for Medical related field or B.Sc courses.If you are from commerce field then you may go for B.Com Honours.If you are from Humanities stream then you may go for BA courses.The students of Science and Commerce can go for BA courses as well. You may go for BBA,BCA,CLAT and many more.The list is endless!You got to decide on what you really wish to pursue.
Hope this helps.
Good luck.