Its not that difficult.
Pure Science is exploration. You explore an area without knowing what the end results would be. Infact you may figure out after an year that you cant make more headway and switch to another area. Pure Science is more of discovery for the sake of building more knowledge in different areas of science.
Take Astrophysics for example. There are many of them who have discovered new stars or Exoplanets or even explained formation of Black Holes. These are areas of exploratory research which dont have any pre-defined goals. Getting funding is a challenge because the real world applications of your research are unknown.
On the other hand, Applied Research and Engineering have an end goal because they use the knowledge gained from pure science to innovate the discovery into an invention. Many industries are willing to sponsor these inventions through grants and if these inventions are successful they end up as an engineered product.
So if you love the thrill of exploratory research which can take you anywhere go for it. There is lots of uncertainty and less money. However if you are more comfortable with goals and want to work on more practical applications that relate to real world pick Applied Research or Engineering.