Your application can call DynamoDB via the public endpoint (dynamodb.us-east-1.amazonaws.com). But if you're in a VPC (i.e. practically all AWS workloads in 2021), you have to route to the internet (you need public subnet(s) I think) to make that call.

VPC Endpoints create a DynamoDB endpoint in your VPC, from the documentation:

"When you create a VPC endpoint for DynamoDB, any requests to a DynamoDB endpoint within the Region (for example, dynamodb.us-west-2.amazonaws.com) are routed to a private DynamoDB endpoint within the Amazon network. You don't need to modify your applications running on EC2 instances in your VPC. The endpoint name remains the same, but the route to DynamoDB stays entirely within the Amazon network, and does not access the public internet."

I call my DynamoDB tables via the public endpoint and it was severely impaired - high error rate and very high (second) latency.

From within a VPC, you can either access DynamoDB via its public internet endpoints (eg, dynamodb.us-east-1.amazonaws.com, which routes through an Internet Gateway attachment in your VPC), or via a VPC endpoint for dynamodb that's directly attached to your VPC. The latter is useful in cases where you want a VPC to not be connected to the internet at all, for example.

VPC Endpoint is a feature of VPC: https://docs.aws.amazon.com/vpc/latest/privatelink/endpoint-...