Concatenate each column value into a string for a subquery - string

Question

All I've done a lot of background reading on this on and off for the past day or so and I'm none the wiser on how to achieve this.
I have looked on this site and found ways of concatenating multiple rows into one column however what I'm after is a bit more bespoke, please help...
I have two tables - one is a list of people and details about them such as name etc and a person reference.
The second contains a number of alerts about a person, one person can have multiple alerts. This would contain a person reference and the type of alert they have in a string.
I want to join these two tables using an inner join on the person reference.
I next want to find all of the alerts for each person and concatenate it into a string and show this as the "All alerts" column.
So I will end up with the following output:
First Name | Surname | All Alerts
-----------+---------+--------------------------
Tony | Stark | Alert 1, Alert 2, Alert 3
I can get as far as going through all of the alerts in the alerts table and put the alerts for every person into a string, obviously I need a concatenated value for each person, and haven't figured out how to do this.
I've spent a day on this and looked into XMLPath solutions and using CTE, CROSS APPLY and subqueries to specify the where clause. I am a little lost.
DECLARE #ConcatenatedVals VARCHAR (255)
SET #ConcatenatedVals =
(
DECLARE #AllAlerts VARCHAR(8000)
SELECT #AllAlerts = COALESCE(#AllAlerts + ', ', '') + personAlert
FROM Alerts
SELECT #AllAlerts AS 'All Alerts'
)

Answer 1

I found the solution for this posted here:
https://www.simple-talk.com/sql/t-sql-programming/concatenating-row-values-in-transact-sql/#Toc205129480
This referenced a solution by Adam Machanic
Also, stuff is actually a function, not seen this before:
SELECT p1.CategoryId,
stuff( (SELECT ','+ProductName
FROM Northwind.dbo.Products p2
WHERE p2.CategoryId = p1.CategoryId
ORDER BY ProductName
FOR XML PATH(''), TYPE).value('.', 'varchar(max)')
,1,1,'')
AS Products
FROM Northwind.dbo.Products p1
GROUP BY CategoryId ;