die Blase
blister
A small swelling on the skin filled with fluid, often caused by friction or a burn.
Von den neuen Wanderschuhen habe ich eine Blase am Fuß bekommen.
I got a blister on my foot from the new hiking boots.

blister / bladder / bubble
Loading your saved state.
blister
A small swelling on the skin filled with fluid, often caused by friction or a burn.
Von den neuen Wanderschuhen habe ich eine Blase am Fuß bekommen.
I got a blister on my foot from the new hiking boots.

The noun 'die Blase' (blister / bladder / bubble) is related to the verb 'blasen' (to blow). The basic idea is always something that is filled with air or liquid and is therefore rounded.
Der Wind bläst heute sehr stark.
The wind is blowing very strongly today.
The context always reveals which meaning of 'Blase' is meant. Words like 'Fuß' (foot) or 'Haut' (skin) point to a blister, 'Seife' (soap) to a soap bubble, and 'Immobilien' (real estate) or 'Aktien' (stocks) to an economic bubble.
Autsch, ich habe eine Blase an der Ferse.
Ouch, I have a blister on my heel.
A blister on the skin is something you 'have' or 'get'. A typical expression is 'sich (Dativ) eine Blase laufen' (to walk oneself into getting a blister), when you get one from walking too long.
Bei der Wanderung habe ich mir eine große Blase gelaufen.
I got a big blister from the hike.
The expression 'Die Blase drückt' (the bladder is pressing) is a colloquial and indirect way of saying that you urgently need to go to the toilet.
Können wir bald eine Pause machen? Meine Blase drückt.
Can we take a break soon? I really need to go to the bathroom.
In a figurative sense, especially in economics, the expression 'die Blase platzt' (the bubble bursts) is often used. It describes the moment when an overvaluation collapses.
Experten befürchten, dass die Immobilienblase bald platzen könnte.
Experts fear that the real estate bubble could burst soon.
foam
'Blase' and 'Schaum' can both have to do with air or gas in a liquid. A 'Blase' is a single small sphere of air or gas. 'Schaum' is a whole mass of many small bubbles, for example on soapy water, beer, or ocean waves. Learners may confuse the words because foam is made up of many bubbles. If you mean a single round shape, you say 'Blase'. If you mean the white or airy mass, you say 'Schaum'.

Im Glas steigt eine kleine Blase nach oben.
A small bubble rises to the top in the glass.
Auf dem Kaffee liegt viel heller Schaum.
There is a lot of light-colored foam on the coffee.