Posto vs. sedile
'Posto' and 'sedile' are Italian words that can both be translated as 'seat' in English, but they have different uses and connotations.
Posto
'Posto' is a more general term that can refer to any place where one can sit or a designated spot for sitting. It can also mean 'place' or 'position' in a broader sense.
Ho prenotato un posto a teatro.
(I've booked a seat at the theater.)
C'è un posto libero sul treno?
(Is there a free seat on the train?)
Questo è il mio posto di lavoro.
(This is my workplace.)
Sedile
'Sedile' specifically refers to the physical seat or chair itself, often in vehicles or furniture.
Il sedile della mia auto è molto comodo.
(The seat of my car is very comfortable.)
Abbassa il sedile della bicicletta.
(Lower the bicycle seat.)
I sedili in prima classe sono più larghi.
(The seats in first class are wider.)
Summary
While 'posto' is a versatile word that can mean a seat in the sense of a place to sit or a general position, 'sedile' specifically refers to the physical seat or chair. Use 'posto' when talking about reserving a seat or occupying a space, and 'sedile' when referring to the actual seat structure or cushion.