Can someone explain what bp should be, and what diastolic and systolic mean?

I'm wondering what blood pressure readings actually mean and how to read it, my first i was induced due to gestational hypertension, but no one explained what it was or anything, what my bp should have been etc. Looking back I now realise I often had symptoms of this, sudden swelling of my feet, occasionally dizzy and feeling really hot, blurred vison at times. I'm thinking of buying a home bp monitor to keep an eye on my bp this time round, especially as I had some of these symptoms for a while before having bub but never metioned them as by the time my monthly appointment came I'd forgotten. Either that or I got the 'thats normal in pregnancy' excuse. So can someone explain it to me please? I appreciate any advice ☺