Vedere vs. guardare
In Italian, vedere and guardare both relate to the sense of sight, but they are not interchangeable. The main difference lies in intention and focus: vedere is the passive act of seeing, while guardare is the active and deliberate act of looking at or watching something.
Vedere
A1The verb vedere means to see and describes the passive, often involuntary, ability to perceive something with your eyes. It refers to what your eyes register, whether you intended to look at it or not. It can also be used figuratively to mean to understand or to meet.
Mentre camminavo, ho visto un mio vecchio amico.
(While I was walking, I saw an old friend of mine.)
Senza occhiali non vedo bene da lontano.
(Without glasses, I can't see well from a distance.)
Hai visto le mie chiavi da qualche parte?
(Have you seen my keys anywhere?)
Adesso vedo qual è il problema.
(Now I see what the problem is.)
Domani vado a vedere i miei nonni.
(Tomorrow I'm going to see my grandparents.)
Apri la finestra e dimmi cosa vedi.
(Open the window and tell me what you see.)
Non vedo l'ora di andare in vacanza.
(I can't wait to go on vacation (literally: I don't see the hour).)
Guardare
A1The verb guardare means to look at or to watch and implies an active, intentional, and focused action. When you guardare something, you are deliberately directing your gaze and attention towards it for a period of time.
Guarda che bel panorama da questa montagna!
(Look at what a beautiful view from this mountain!)
Mi piace guardare le stelle di notte.
(I like to watch the stars at night.)
Il bambino guarda i cartoni animati ogni pomeriggio.
(The child watches cartoons every afternoon.)
Perché mi guardi in quel modo?
(Why are you looking at me that way?)
Guarda attentamente le istruzioni prima di iniziare.
(Look carefully at the instructions before you start.)
Il gatto sta guardando un uccello fuori dalla finestra.
(The cat is watching a bird outside the window.)
Dobbiamo guardare entrambi i lati della strada prima di attraversare.
(We have to look at both sides of the street before crossing.)
Summary
In essence, use vedere for the passive sense of sight (to see), similar to what your eyes perceive without conscious effort. Use guardare for the active and intentional act of directing your attention to something (to look at, to watch). You might vedere a flash of light in your peripheral vision, but you would turn your head to guardare what caused it.