Better understanding of getInitialProps, getStaticProps and getServerSideProps

[hk86]

I'm new to Next.js (I use 9.4) and currently I try to get an better understand on how it works. In my /pages components I use getStaticProps and getServerSideProps. From the documentation I understood that these never run on the client. getStaticProps is used when it is rendered statically and getServerSideProps is used on every request. Besides these functions I use getInitialProps in my extended App component in _app.js. I use it in order to fetch the localization strings and pass it to the components. I would assume that getInitialProps runs only once during build and then the information is made available to the pages statically. Is that assumption correct?