diff --git a/src/worker/worker.rs b/src/worker/worker.rs
index 3a4f516..795aefe 100644
--- a/src/worker/worker.rs
+++ b/src/worker/worker.rs
@@ -7,6 +7,9 @@ use super::handler::Handler;
 use crate::error::HandlerError;
 use crate::model::*;
 
+// Queue is a simple queue data structure.
+//
+// It is protected by a mutex and avoid to be CPU consuming with `not_empty` condvar.
 pub struct Queue<T> {
     content: Mutex<VecDeque<T>>,
     not_empty: Condvar,
@@ -30,6 +33,7 @@ pub enum WorkerStatus {
     Stopped,
 }
 
+// Worker holds the computation in thread with a status.
 struct Worker {
     id: u32,
     manager: String,
@@ -55,6 +59,9 @@ impl Worker {
     }
 }
 
+// Manager is a pool of workers and holds a queue containing `Job` to run.
+//
+// TODO: to handle more message, replace the trait with a `Message` trait.
 pub struct Manager<T: Runner> {
     name: String,
     workers: Vec<Arc<Mutex<Worker>>>,
@@ -111,6 +118,7 @@ impl<T: Runner + Send + 'static> Manager<T> {
         }
     }
 
+    // subscribe subscribes to a `Receiver` channel.
     pub fn subscribe(&self, receiver: Receiver<T>) {
         let queue = self.queue.clone();
         thread::spawn(move || loop {