Answer will get very long so limiting it with a few 'hoon' is form of 'to be' other forms are hai, hain, ho when sentence starts with 'main' (I) and it is 'present tense' you always end the sentence with 'hoon'; u can think it is similar with english 'am' ('I' is male) main jaata hoon. i go. main khaata hoon. i eat. main bharteeya hoon. i am an Indian. main jaa raha hoon. i am going. note that if sentence doensnt start with 'main', ot doesnttake hoon as an ending. if u end sentence with hoon, it is understood that u are talking about urself e.g. jaati hoon. i go.(f says) ho when sentence starts with 'tum' (you; informal) and it is 'present tense' you always end the sentence with 'ho'; (to a 'male') tum jaate ho. u go. tum khaate ho. u eat. tum bharteeya ho. u are an Indian. tum jaa rahe ho. u are going. sometimes it is used with aap as well. replace tum with aap and sentences are still correct in colloquial form. i would suggest use of 'hain' which is better and more correct ho is also a form of verb 'hona' one of its many meanings and well understood one is, 'to happen' ho in this sense may be like a imperative verb. like one fom of imperative form of verb 'jaana'(to go) is 'jaa' (go) there are more ways of politely expressing the same for other verbs but ho doesnt have that complicacy.(description is incomplete) any sentence not starting with tum/main will take up hai as ending like mujhe karna hai- i have to do.(mujhe karna padega/mujhe karna hoga) tumne/maine kaha hai- you/i have said hai - u can think it of as english 'is' and also it is used in sentences similar to above examples but for third person, like- he,she,it, and singular subjects like any noun ladka khata hai. boy eats wah jaata hai. he goes. wah jaati hai. she goes. tumhara naam kya hai? what is ur name. wah engineer hai. he/she is engineer. hain- u can think it as english are. 'aap'(you with respect) should take up 'hain' as ending aap jaate hain. u go. (with respect) aap yahan aa rahe hain. u r coming here. aap russian hain. u r russian. aap kaise hain? how r u? etc. for third persons as well sabhi jaa rahe hain. everyone is going. bachche khel rahe hain. children are playing...etc and many more, the answer it not thoroughly thought so there may be other cases which i might have forgot to touch here. but i guess it gives u a fair idea.