Tie is a less formal, more common word. Necktie is more specific and formal. Necktie is also used in situations where the word tie might be ambiguous - as in, "Tie your necktie, man, it's time to go!" Though "I need to tie my tie" is often heard, it's got a bit of a humorous ring.
'b' and 'v' have sounds so much similar, With a slight difference, in fact in latin america practically there is no difference, reason why there are enough problems of orthography precisely with these vowels. There are words like "Baso = base" and "Vaso = glasses" that are phonetically practically the same in latin america
In fact, it means "It is" in this sentence. There is no direct translation for "it" in Spanish. "It" is only translated into Spanish when it refers to a previously mentioned thing.
Do you have my red car? - Yes, I have it.
¿Tienes mi coche rojo? - Sí, lo tengo
The "lo" means "it" (only for masculine nouns) which refers to the car. "Lo" can also mean "him" when "him" is the object of the sentence.
She talks to the boy, but I see him - Ella habla con el niño, pero lo veo.