Depends on the job ;-) For all non-computational linguists I'll go ELI5 on this: For machine translation I work mostly with the moses toolkit[1] with IRSTLM as language model. This toolkit is made for statistical machine translation - so you need a lot of data and a parallel corpus (identical texts in both languages e.g. stuff you find in those little "phrases for travelling" booklets). If you're running a Unix-System it's pretty easy to get started (baseline) - you can use the europarl-corpus for some nice experiments (what about your own Portuguese-German translator? ;-) There is also a pretty nice tollkit named "apertium"[2] - this is about rule-based MT, so you don't need a lot of data, but you need a comprehensive grammar (constisting of a lexicon and grammar rules). For other stuff I do there are tons of different methods and approaches each- from formal/funcitonal grammar up to machine learning/deep learning techniques (Naïve Bayes classifier, Support vector machines etc.) If you're (or others) are interested, I could post some interesting links for Natural Language Processing (maybe a new Tag for that?)