What is a bounce rate in my Google Analytics website statistics?

No, your website visitors aren’t made of rubber. Bounce rate reflects the percentage of website visitors who leave a website without visiting a second page. They only viewed the page they landed on.
Is a high bounce rate bad?
Like most things it depends.
If a visitor was able to get what he or she needed from a single pageview, such as getting your phone number or location, a high bounce rate isn’t worrisome. However, if you are expecting user behavior to include multiple pageviews, such as an ecommerce website, it is.
Whether or not a high bounce rate should be concerning really comes down to the amount and type of information available to visitors on the page they land on. Some websites spread out information into different pages, some like to concentrate it onto a single page or a small number of pages. The latter is increasingly becoming common with a greater focus on continuous scrolling.
Generally, visitors to a website already have some familiarity with that company. They may not need to go exploring multiple pages to learn about you and your offerings. They may only be there to find out how to contact you. This is why all pages, especially your homepage, which is the most common landing page, should have plainly posted contact information.