SQL Server Update one row blocking

I use Sql Server and have simple table:

Person(ID bigint,Name nvarchar(255))

It contains 1000 rows(for example). I'm using SQL query:

Update Person
Set Name = 'Jason' where Id = 100

I want to understand - how Sql Server will do read/write locking. Will it block one row (which i'm updating) or it'l block all Person table?

Will the situation change if i will use query?

Update Person
Set Name = 'Jason' where Name = 'Piter'