Premium Economy Explained
While economy-class tickets have become more affordable, this affordability has often comes at a cost: the comfort of the passenger. For this very reason, airlines have launched the new premium economy class. This category of airline ticket offers passengers a class of service somewhere between economy and business. Essentially passengers get a little more comfort for a little more money, making it the perfect choice for those that don't want to, or can't, fork up the money for a business class seat but would like to experience a higher level of in-flight offerings. What the additional costs and comforts are vary from airline to airline, 
but typically passengers can expect the following on long-haul flights:

More leg room and wider seats - Premium economy seats offer an average of 15 cm (just under 6 inches) more pitch than economy class seats, making it more comfortable for even the tallest passenger to stretch out. 
In addition, most seats are between 2 cm and 3.8 cm wider than the economy-class average (around 1-2 inches more). 
Though this may not seem significant, it actually makes quite a difference when it comes to comfort. Finally, passengers flying in this new premium class have a footrest and a 20 cm seat recline so that they can lie slightly flatter than they would in economy class.
A separate cabin and dedicated check-in - It is rare to find families with small children and infants in this class, so the separate cabin can make for a more peaceful journey. The dedicated check-in counter also means less queueing.
Bigger entertainment screens, tray tables and USB ports - Most carriers offer a larger in-flight entertainment screen and some even offer noise-cancelling headphones when flying premium economy. In addition, each seat has at least one USB port and a dedicated universal power socket. 
This way passengers who prefer to catch up on their favourite show can bring their own in-flight entertainment along in the form of a tablet or laptop. The larger tray table also makes it a lot more comfortable for passengers who want to use the flight to get some work done and use the tray table as a workstation.
Good food and good service: Here each airline adds its own personal touch. For example, British Airways provides a three-course meal with business class menu options and meals are served on china. 
Passengers also get linen napkins and enjoy a full complimentary bar service. 
Singapore airlines also lets passengers choose a special meal from the 'Book the Cook' pre-order service 24 hours before the flight.

Other perks: Since this is not a standardised service across airlines, carriers offer a variety of perks for passengers in this class. 
Some of these perks include additional baggage allowance, extra miles, airport lounge access and much more.

Note :- The above offer is subject to availability at the time of booking