They both mean ' to remember' but “记住" could also mean 'to bear in mind' or 'to learn by heart'.
记得
means to remember , to call back to mind , to keep in memory:
越是老八辈子的事,老年人记得越清楚。
Yuè shì lǎo bābèizi de shì,lǎoniánrén jì de yuè qīngchu.
The more remote things are, the more clearly old folks can remember them
记住
means to remember; learn by heart; bear in mind;memorize
你千万要记住老师的话。
Nǐ qiānwàn yào jìzhù lǎoshī de huà.
Be sure to remember what the teacher said.