what does "debo" mean?
Deber is the verb you add to make it conditional or that you should do something.
So in this case debo decir is "I should say..."
Deber also means "to owe". It doesn't fit in this context, but, debo itself could mean "I owe...".
Here is the link to the Conjugation of "deber:"
Or just go to the link at the top of the page: "More", than "conjugation". You can type in the infinitive, if you know it (in this case "deber") or any form of the verb, (like "debo").
In case you are wondering, your whole phrase would be translated as "it is for that reason I should say...".
Hope this is helpful. Lots of great tools on this website.
Deber can also be used as an order.
Debes comer means "you must eat"
It is most definitely not an order (nor is "you must eat").. It is an assertion/statement that you have a moral/or whatever obligation to eat.In language learning sites (assuming that they observe the usual linguistic conventions) "command" has a very specific meaning ("an imperative") and (in many languages) an equally specific grammatical form.
You may, if you wish, interpret interpret such moral injunctions as commands but your decision does not mean that they are (in any grammatical sense, commands).
P.S. "debes comer" does not mean "you must eat" but, rather, "you ought to eat".