Because "speak" and "talk" in english are somewhat interchangable, you can translate both, but for "talk" the dutch word "praten" would be a better translation.
Dutch is my first language and you use speak - spreken in a more formal setting and talk-praat in a casual setting
is this perhaps where english gets the informal phrase 'to pratel off' about something?
Usually adding the 'en' makes it plural. Do we add the 's' here because the singular 'jongen' already ends in 'en'?
het is used for 'common' nouns, and 'de' for neutral. in the past, Dutch had 3 grammatical genders, like german. But the masculine and feminine forms collapsed into one single category. It's important not to confuse grammatical gender with real, human genders or any notion of 'masculine/feminine' characteristics. you just have to learn what article matches each noun. it's important because the grammatical gender of a noun influences other parts of a sentence that must agree with it.
also, all plural forms use 'de' EVEN IF the singular form takes 'het'
I think you have it the wrong way round there. It is 'de' for common nouns, and 'het' for neuter nouns.
it just is a way to refer to that noun category that USED to be 'masculine' and 'feminine' separated, but those are now joined, so it had to be re-named. it's just the translation. like how french has 'le masculin' et 'la feminine', it's just called 'common' and 'neuter' (to reflect how 'common' used to be 2 separate categories)
Please read Emmet's comment above.
The both mean the.
Het is used with neuter gender words.
De is used with common gender words and with plurals.
For more information and some guidelines to distinguish both groups of words, please read: