What type of isomers are the following two compounds?

What type of isomers are the following two compounds?They do not seem to be geometrical isomers as the methyl groups at terminal position are not in same plane as such.Are they conformers?


[![enter image description here](https://i.stack.imgur.com/K4qvw.png)](https://i.stack.imgur.com/K4qvw.png)


