This is the 604th most frequent Slovenian word.
aleš
"Aleš" is a Slovenian male given name, equivalent to "Alex" or "Alexander" in English.
In this sentence, 'Aleš' is used as a proper noun, specifically as the name of a person.
Aleš hitro teki po parku.
Aleš quickly ran through the park.
Here, 'aleš' is used metaphorically or idiomatically to imply the core or essence of something.
To ni aleš vsega, kar imam povedati.
This is not the crux of everything I have to say.
In this case, 'Aleš' still functions as a proper noun, referring to a personal name, but it's embedded in a metaphorical expression.