überall
everywhere
In all places; at every location.
Im Frühling blühen überall bunte Blumen.
In spring, colorful flowers bloom everywhere.

everywhere
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everywhere
In all places; at every location.
Im Frühling blühen überall bunte Blumen.
In spring, colorful flowers bloom everywhere.

The word is a compound of 'über' (over) and 'all' (all). It literally means 'over everything' or 'in all places,' which makes it easy to remember.
Nach dem Sturm lagen überall Äste auf den Straßen.
After the storm, branches were lying everywhere on the streets.
As an adverb, 'überall' can appear in different positions in the sentence. It often appears at the beginning of the sentence for emphasis (then the verb follows) or in the middle of the sentence after the verb.
Überall auf der Welt gibt es interessante Kulturen zu entdecken.
Everywhere in the world, there are interesting cultures to discover.
'Überall' is frequently combined with 'fast' (almost) to soften the statement somewhat ('fast überall'—almost everywhere). It can also introduce a relative clause with 'wo': 'überall, wo ...' (everywhere where/wherever ...).
Fast überall in der Stadt gibt es kostenloses WLAN.
There is free Wi-Fi almost everywhere in the city.
somewhere
'überall' and 'irgendwo' both refer to places, but they mean very different things. 'überall' means: in all places or at every location. 'irgendwo' means: in one place, but you do not know exactly where, or it is not important. They can be confused because neither gives a precise location. The difference is: 'überall' is a lot, while 'irgendwo' is only one unspecified place.

Nach dem Einkauf lagen die Taschen überall in der Küche.
After the shopping trip, the bags were lying everywhere in the kitchen.
Der Schlüssel muss irgendwo im Flur sein.
The key must be somewhere in the hallway.