Generally this code is printed on plastic bottles in a triangle mark. This code describe the type of material or resin used in making of that plastic thing ie container,buckets,mugs...
Code-1 PET or PETE ( Polyethylene Terephthalate)
Air can not go inside in such things that is why cold drinks bottle,Jar... are made of such materials.
Code-2 HDPE (High Density Polyethylene)
This is mostly used type of plastic.It is cheap and can be recycled.
Code-3 PVC ( Polyvinyl Chloride)
This is hard type of plastic used in pipes,toys.... it is not used to keep eating things.
Code-4 LDPE( Low Density Polyethylene)
This type of plastic is very thin therefore it used in press able things like tomato ketchup, honey...
Code-5 PP (Polypropylene)
This type of plastic used in making containers for microwave.It is also used in making containers for keeping medicines.
Code-6 PS (Polystyrene)
This type of plastic is used in making disposable glass,bottles,cups,plates...
Code-7 Other
This sign is used on such things, which are made from unknown plastic.It means information about the plastic used in such materials is unknown.