For Any iMac Users: New iMac Sr. Citizen Question Re Icons

[BOBRR]

Hello,

Brand new iMac desktop user.
Sure is a lot to learn; not too sharp with this "stuff," frankly.
SDr. Citizen now, very, so will blame my ignorance on that.

Have Thunderbird with eternal September running on the new iMac.
Seems to have all of my old Windows 10 Folders, etc. Amazing !

a. Question: on my iMac Desktop, there are two Icons I am not sure about:

One says: Thunderbird 195 MB
The other says: Thunderbird 52.5.2.dmg 79 MB

What are these, please ?
If I want a "clean" Desktop, where should I move them to ? The Finder, or...?
Create a Folder, and move the Folder "somewhere" ?

b. When I click on Thunderbird in the Dock, sometimes the program opens right up, other times
another what seems to be a small window with a Thunderbird logo, and an arrow pointing to a Folder
in the window saying Applications.
What is this, and is it possible to Always go to Thunderbird by just clicking the Dock icon, rather than this extra step ?

c. Let me ask this also, please re eternal-september: I use the Usenet a lot.
Seems to work just fine.

But I also seem to have below eternal-september another line that says "news"
What is this please ?
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BTW: anyone find an APP that works for making ALL the Thunderbird page fonts bigger ?
Eyes not that good anymore. Can't help thinking there must be some way of doing this ?

Much thanks,
Appreciate the help,
Bob

[tanstaafl]

"BTW: anyone find an APP that works for making ALL the Thunderbird page fonts bigger ?"

See http://kb.mozillazine.org/Bad_Eyesight_-_Thunderbird . Use the Theme font & size changer add-on to change the font/size for everything except messages. Use the built-in features at Preferences -> Display -> Fonts -> Advanced to change message font/size.

Unfortunately I can't help you on the Mac desktop questions as I'm running Windows 10.