There're 4 type of FIR to chose from

1. symetry ,even
2. symetry ,odd
3. antisymetry, even
4. antysymetry, odd

Also, there are many type of window like rectangular, Hanning, Kaiser,etc So how to use a window function to design the N-length filter and what's the point of doing it? That's what my teacher ask me to do but I don't understand the reason

What I confuse here is that for example I want the ideal filter $H(\omega)$ that have passband in $\omega\_a <\omega<\omega\_b$ then what I need to do is just use the inverse Fourier transform to the frequency response of the ideal filter to find $h[n]$ that is infinite then use the window function to make it finite. Then what's the point of make it look like the form of one of those 4 type? Moreover, what I need to do after doing inverse Fourier Transform and window function to make it in the form of FIR digital filter with N-length?