How translation works
Translation reads a coding sequence three bases (a codon) at a time and maps each codon to an amino acid using the genetic code. ATG encodes methionine and is the usual start codon; TAA, TAG and TGA are stop codons, shown as *.
Why six frames?
Without annotation you do not know where a gene starts or which strand it is on. A sequence can be read starting at base 1, 2 or 3 on the forward strand and likewise on the reverse complement, giving six possible reading frames. The frame that produces a long stretch without stop codons is usually the real one.
Learn the method properly. Python for Bioinformatics: Programming taught through biological problems, from parsing FASTA to tested, shareable tools. View the course.