I am student of MA and i need your help to know about the praat software. i am stuck in my research in last section. If any one hear to know so i thoroughly and rigorously sorry to say and please help me in this thing.
This is not a question about Praat, it is a question about phonetics, which you could answer using Praat (or some other analytic device). The primary question is 'Is there a dependable phonetic correlate of being a consonant versus being a vowel?': the answer is 'Mostly, not entirely'. The way you figure out what those correlates are is to inspect a range of samples of speech where you know what sounds are consonants and what sounds are vowel (for example, in your native language).
In Praat, you would use the sound editor to inspect the waveform and corresponding spectrogram. You can select any continuous portion of the window and then play the whole window, the selection, the part before the selection of the part after the selection (you can also select just one instant). What you would want to do is play the parts of the waveform, let us say [kisa], to see where the segment of interest is (let's say [s]). Perhaps by trial and error, you select [s], because the part before the selection sounds like [ki] and doesn't sound like it includes part of [s], the selection sounds like [s] (not [ĭsă]), and the part after sounds like [a], not [sa]. Exact selection isn't crucial, you just need to know what neighborhood [s] is in.
Now that you can see what part is [s] you can also see, from the spectrogram (if you know how to interpret the display), what its phonetic characteristics are, and how different they are from the preceding or following vowel. You do this many times, and you come up with a general theory of what is true of consonants, and what is true of vowels. You can also read the phonetic literature to see what suggestions scholars have made, starting perhaps with Potter, Kopp & Green (1947) Visible speech.
Vowels are produced with a more open vocal tract, which means that there are clearer resonances of higher amplitude, and their articulation is more constant over time. This is a very general picture which takes you only so far, and then you run into problem consonants (j w ɹ) and vowels (ṳ).