El carrito portaequipajes está junto a la consigna.

Because this sentence describes location, and in Spanish location is normally expressed with estar, not ser.

• está junto a la consigna = is next to the left-luggage office / baggage check
• ser is usually for identity, origin, characteristics, time, etc.

So:

• El carrito portaequipajes está junto a la consigna. = the luggage cart is next to the left-luggage office.
• Using es here would sound wrong in standard Spanish.

Junto a means next to, beside, or right by.

It suggests closeness, usually more specifically than cerca de.

Comparison:

• junto a = next to / right beside
• al lado de = next to / at the side of
• cerca de = near

So está junto a la consigna gives the idea that the cart is right next to the consigna, not just somewhere nearby.

In Spain, la consigna often means a left-luggage office, baggage check, or sometimes luggage lockers in places like train or bus stations.

This can confuse English speakers because consigna can mean different things in other contexts, such as:

• a slogan
• an instruction
• a watchword

But in this sentence, with luggage and a cart, it clearly refers to the place where baggage is stored temporarily.

Carrito is the diminutive form of carro, and here it means small cart or trolley.

In Spain, carrito is a very natural word for a small wheeled cart. In this context, it refers to a luggage trolley/cart.

A few related words:

• carro = cart, wagon, or in some countries even car
• coche = car in Spain, not a luggage cart
• carrito = little cart / trolley

So carrito is the natural choice here.

Portaequipajes is a compound noun meaning luggage carrier or luggage rack/cart depending on context.

It comes from:

• porta- = carries
• equipajes = luggage

Spanish often forms these compound words as a single unit:

• abrelatas = can opener
• sacacorchos = corkscrew
• portaequipajes = luggage carrier

In carrito portaequipajes, the second noun works almost like a label telling you what kind of cart it is: a luggage cart.

Spanish usually uses articles more often than English.

Here:

• El carrito portaequipajes = the luggage cart
• la consigna = the left-luggage office

Each noun phrase needs its own article:

• el for the masculine singular noun carrito
• la for the feminine singular noun consigna

You generally cannot omit them here in normal Spanish.

The article tells you:

• el carrito = masculine
• la consigna = feminine

Also:

• carrito ends in -o, which is often masculine
• consigna ends in -a, which is often feminine

These are common patterns, though not absolute rules.

If you wanted to describe them with adjectives, the adjectives would agree:

• El carrito está vacío.
• La consigna está cerrada.

Yes, el carrito de equipajes would be understandable and natural in many situations.

Difference in feel:

• carrito portaequipajes sounds a bit more like a fixed compound label, similar to luggage trolley
• carrito de equipajes is a more transparent phrase meaning cart for luggage

Both can work, but the original sentence uses portaequipajes as the standard compound form.

Because portaequipajes functions as a compound noun that directly describes the type of cart.

Spanish sometimes puts two nouns together like this, especially when one is a set expression or a compound label:

• coche cama
• tren bala
• carrito portaequipajes

In other cases, Spanish uses de:

• carrito de compra
• bolsa de viaje

So this is something you often learn as part of the vocabulary item itself.

A simple pronunciation guide is:

por-ta-e-qui-PA-jes

A few helpful points:

• The stress falls on pa: portaequiPAjes
• The j in equipajes is pronounced like a strong English h, but rougher: pa-hes
• The sequence tae is pronounced smoothly across syllables: por-ta-e-...

A rough English approximation would be: por-tah-eh-kee-PAH-hes

Yes, -ito is a diminutive ending, and it often suggests:

• small size
• a lighter or more familiar tone
• sometimes affection

So carrito literally suggests a small cart.

However, in many everyday expressions, the diminutive becomes the normal word people use, so it does not always strongly emphasize smallness. In this sentence, it most naturally just means cart/trolley.

Yes, but it means something slightly different.

• El carrito portaequipajes está junto a la consigna.
  = The luggage cart is next to the consigna.
  You are talking about a specific cart.

• Hay un carrito portaequipajes junto a la consigna.
  = There is a luggage cart next to the consigna.
  You are introducing its existence, not identifying a specific known cart.

So both are correct, but they do different jobs.

Yes. In most situations, junto a and al lado de mean nearly the same thing.

• está junto a la consigna
• está al lado de la consigna

Both mean it is next to the consigna.

A learner can safely use either one. Junto a may sound a little more compact or slightly more formal in some contexts, but both are very common.