Camicia vs. maglia
While both maglia and camicia can be translated to the English word shirt, they refer to fundamentally different types of men's clothing based on their construction, fabric, and style.
Camicia
The word camicia specifically refers to a traditional, button-up dress shirt that features a collar and cuffs. It is almost always made of woven fabrics, such as cotton or linen, and is the standard garment worn with suits or in formal, business, and smart-casual settings.
Indosso sempre una camicia bianca per i colloqui di lavoro.
(I always wear a white shirt for job interviews.)
Questa camicia di lino è perfetta per l'estate.
(This linen shirt is perfect for the summer.)
Ricordati di stirare la camicia blu prima del matrimonio.
(Remember to iron the blue shirt before the wedding.)
Ha sbottonato la camicia perché faceva molto caldo nell'ufficio.
(He unbuttoned the shirt because it was very hot in the office.)
Mio padre preferisce indossare una camicia a maniche corte in vacanza.
(My father prefers to wear a short-sleeved shirt on vacation.)
Maglia
The word maglia is a broader term used for any knitted pull-over top, which can range from a casual shirt to a sports jersey, an undershirt, or a light sweater. Unlike a camicia, a maglia is made of knitted or elastic material, is generally worn casually, and lacks a full vertical row of buttons.
La squadra ha presentato la nuova maglia per la prossima stagione.
(The team presented the new shirt for the next season.)
Mettiti una maglia intima sotto perché oggi fa molto freddo.
(Put on an undershirt underneath because it is very cold today.)
Questa maglia a righe ti sta molto bene con quei pantaloni.
(This striped shirt looks very good on you with those pants.)
Purtroppo ho macchiato la mia maglia preferita con il caffè.
(Unfortunately I stained my favorite shirt with coffee.)
Durante la corsa indossa sempre una maglia traspirante.
(During his run he always wears a breathable shirt.)
Summary
To summarize, choose camicia when talking about a woven, button-up dress shirt with a collar, and use maglia for comfortable, knitted pull-over garments like casual shirts, undershirts, and athletic jerseys.