As part of my job, I often interpret and translate.
If someone asks me what it is like to do simultaneous interpretation (SI) I always tell them to watch the television news and repeat everything verbatim – as soon it is said. It is not that easy. SI is like doing that, but with the added complication of repeating it in another language. The amount of concentration it takes is extremely draining and one mistake can cause a huge international incident so you have to be really careful, particularly with idioms and jokes.
Consecutive translation (CI) is when the person speaking stops at intervals and you interpret these blocks of speech after they have stopped talking. Short CI (a few minutes at a time) you can do from memory but long CI you have to write things down and then use the notes to read back after the person has finished their block. With both of these you need a good memory.
Whispered interpretation is when you sit near someone and speak in a low voice (rather than actually whispering). This is usually done when someone needs to understand what is being said (at a conference for example) but not contribute.
If they ask me what it is like to translate, I generally say it is like being a detective. Sometimes it is easy and you can just translate directly. But other times if it is very specialized (like translating the technical specifications of a warship or a plane) and you have to research everything to make sure you are doing it correctly. My first step is usually to see if I can find a translation in a dictionary. But with very technical terms it is often not that straightforward. So I then do a Google image search in Swedish and see what it looks like. Then I try to do Google images searches in English which get me nearer and nearer my goal. This would work for a bow thruster tunnel for example but not for anything more unusual. So then you often have to read through technical reports both in Swedish and in English to find a physical description. Or you have to ask the designers if you can get hold of them. When you finally untangle a very knotted sentence full of words you have never seen before and it is laid out before you like a silken skein it is the most amazing feeling!
In translating, it is much easier to translate a well written text to another language than a badly written one. You would assume that if something is worth translating, it would be well written but this is often not the case. Then you almost have to correct it in the original language before you can translate it into the target language. For this, your grasp of the original language needs to be very good.