Sometimes people often confuse about this terminology. so Let's talk about this topic.

FRONTEND Engineers are those who work on front part of the website or we can say the part of the website which Is visible to our eyes.

UX designers are the person who decides whether the button or text field is suitable for the website or not. or from which place the button should be placed for a better user experience.

UI designer decides what will be the colour of the button, image and background for a better user experience.

In a startup usually, one person does all of the work. But in big MNCs, They hire different people for different roles.