One of the points of giving children toys, even from the earliest age, is to stimulate their curiosity and to help them learn about the world. Children love to play, so making play enjoyable enhances the whole learning experience.

As a parent you need to spend time with your child, helping to stimulate curiosity, guiding, and generally interacting. The ability of a child to relate to people is as important of course as an understanding of inanimate objects.
In the first two months of life a baby can only focus on objects 8-10 inches away, so it's necessary to give a baby bright coloured toys of a good size, encouraging the discovery of texture and colour.
Play helps a baby, and then a toddler, to explore, discover, experiment, and practice new skills. A baby will hit something with its hand, then start to touch and feel textures, then begin to grasp, and then finally hold and manipulate objects. When your toddler manages to put a spoonful of porridge into his or her mouth, then that is just one achievement in a long line of increasingly sophisticated ones still to come.
Ideally, once a child becomes a toddler, toys should challenge him but not frustrate, and should be ones that he can play with on his own, but also with another child in order to develop social skills, such as the notion of taking turns. Simple building bricks are one example, and a push or pull along toy is another. Easy jig-saw puzzles with large pieces are helpful in developing motor skills, pattern recognition, and spacial awareness.
As your child grows older he will develop more imagination and more curiosity about the real world. Now he may be delighted by simple kits that help make things, such as a beginner's architect kit with different shaped pieces of plastic and mylar, or easy to build functional kits like the Engino set. This kit helps a child to learn about levers, pulleys, wheels, screws, axles, and other engineering concepts.
A recently introduced toy is the Aerobubbles Play System, which comprises a set of individual air cushions that lock together to form a playhouse, or a boat, for example.
Sets of models are always popular with children, and there is a fine range manufactured by a company called Schleich. One of the exciting ranges of lifelike models encompasses the many varieties of African animals, each constructed from robust resin and carefully hand painted. These give a true representation of the real animals, and there are even trees and plants from the African landscape to go with them.
Another superb range of Schleich models depicts the world of knights which really brings an historical age to life for a child. The ranges includes: a tournament knight in full armour, on horseback, with shield and lance at the ready, a foot soldier wielding a large battleaxe, a knight astride a horse with sword raised, a cross-bowman, a prince of knights seated on a rearing horse, archers, and assorted knights on foot. In addition there are accessories to make a full arena setting. These include a knight's castle with stairs and ladders, a stable, a large wheeled catapult, a decorated tournament tent, a fiercesome dragon, and more.
Play-sets like these are ideal for stimulating a child's imagination and can encourage role playing and foster sharing, and ideas sharing between children.
All these toys are just some examples of the many that are available. Once a parent has an idea of the ways in which a child develops then it is possible to find appropriate toys for each progressive age group.