Bakelite and polythene are both plastics. The one major difference between them is that

The major difference between bakelite and polyethylene is that bakelite is thermosetting and polyethylene is thermoplastic.

Thermosetting and thermoplastic are the two types of plastics. 

• Thermosetting plastics are polymer materials that, once formed and solidified, cannot be melted or reshaped by heating.

Bakelite is a type of thermosetting plastic.

• Thermoplastics are polymer materials that can be softened and molded when heated and can be solidified and re-molded multiple times.

Polythene (also known as polyethylene) is a type of thermoplastic.