The Espresso is made by the Barista and is at its purest form a concentrated coffee hit. It'll be pretty much the cheapest item on a crowded menu of favoured and diluted derivatives which are worth experimenting with. Most commonly the Espresso becomes an Americano, by diluting with hot water. If you ask for a black coffee that's what you're getting. In most cases an Americano is what the white-coffee drinker also wants when they end up ordering a Latte. The Americano comes black but room for milk is an option. A good tasty coffee has a Crèma, a tasty golden layer, on top, contrast that with the thin film around the edges of an instant coffee. The quality of this is a combination of the freshness of the coffee beans and the way the coffee is made.
In some Espresso Bars the Americano can be a rather weak drink, over diluted and verging towards the consistency of an Instant Coffee (though never quite that bad!), requesting a double-shot is well advised, and comes by default at Caffe Nero.
The alternative from Starbucks is a filter coffee. Usually they'll have two coffees brewing as a Freshly Brewed Coffee, a strong fair trade coffee and another blend from around the world. This is a drip coffee rather than made at high pressure like an Espresso. It's a fine drink usually nicer than a weak Americano. The thing to watch for is that drip filter coffee kept warm tends to burn after about half an hour and is then a little unpleasant. Starbucks refreshes theirs every so often, usually keeping only one brewing at a time. It'd be worth requesting the other option offered and waiting a few minutes to have it fresh. At Starbucks this is the next cheapest coffee to an Espresso, and is really what the average coffee drinker wants to drink - white or black.
Both Espresso and Drip coffee can be made at home if you buy the right machinery.