C# - RabbitMQ - Doubts about RabbitMQ Methods

I've implemented a listener service using rabbitMQ. I used a log for show the message body received but i dont know the main purpose for "_channel.BasicAck" and "_channel.BasicConsume" methods and why is in that order.

using RabbitMQ.Client;
using RabbitMQ.Client.Events;
using Serilog;
using System.Text;
using System.Text.Json;

    public class ListenerBackgroundService : BackgroundService
    {
        private readonly ILogger _logger = Log.Logger.ForContext<ListenerBackgroundService();
        private readonly IConfiguration _configuration;
        private IConnection connection;
        private IModel _channel;

        public ListenerBackgroundService(IConfiguration configuration)
        {
            _configuration = configuration;
        }

        protected override async Task ExecuteAsync(CancellationToken stoppingToken)
        {
            stoppingToken.ThrowIfCancellationRequested();

            var consumer = new AsyncEventingBasicConsumer(_channel);
            consumer.Received += async (bc, ea) =>
            {
                var message = Encoding.UTF8.GetString(ea.Body.ToArray());

                var mensaje = JsonSerializer.Deserialize<IntegrationMessage>(message);
                try
                {
                    //Add message parsing and handling logic here
                    _logger.Information(mensaje.Message);

                    _channel.BasicAck(ea.DeliveryTag, false);
                }
                catch (Exception ex)
                {
                    _channel.BasicNack(ea.DeliveryTag, false, false);
                }
            };

            _channel.BasicConsume(queue: "hello", autoAck: false, consumer: consumer);

            await Task.CompletedTask;
        }